The present invention relates to a method and a device for determining the state of a rail stretch, such as a length of elevator guide rail.
Guide rails serve for the guidance of objects, for example the guidance of elevator cars. As a rule, several guide rails are connected end-to-end to form a rail stretch. Elevator cars are usually conveyed suspended by cables and guided by way of guide wheels along the rail stretch. In that case, the rectilinearity of the rail stretch becomes significant, since travel comfort depends thereon. Departures from rectilinearity of the rail stretch lead to vibrations in the elevator car. Even with a long rail stretch and fast elevator cars, for example in tall buildings, such vibrations are strongly noticeable and are perceived as disadvantageous by the passengers.
In order to determine the rectilinearity of the rail stretch in the installed state, measuring of the rail stretch is often done with a plumb bob, for example by cord or by laser. However, these measurements are very time-consuming. For this reason the measuring points are reduced in most cases to the fastening locations of the guide rails. In addition, such measurements must be undertaken at times when the elevator installation is not used, i.e. often at night, which requires night work with extra pay and makes maintenance of the elevator installation expensive. An improvement is desirable in this area.
A solution for that purpose is presented in the EP 0 905 080 European patent document. According to this method, deviations from the rectilinearity of the rail stretch are determined by way of several travel pick-ups fastened to an elongated housing. Magnitudes and position of the deviations are thereupon calculated. The travel pick-ups are mechanical or optical in nature.
A disadvantage of this solution is the high cost of this device.
The present invention concerns a method and an apparatus for determining the state of a stretch of guide rail.
An advantage of the present invention is that it provides a simple, quick and accurate method of determining the state of a rail stretch. This method and the corresponding device shall be compatible with proven techniques and standards of machine construction.
The present invention utilizes three or more transmitters and a receiver in order to determine the position of the receiver with respect to a rail stretch. For example, the transmitters are distributed in any manner in an elevator shaft of the elevator installation and locally fixed. Advantageously, the transmitters are arranged in the elevator shaft at the greatest possible angular spacings from the receiver for a triangulation. The receiver is advantageously moved at a constant spacing with respect to a guide surface of the rail stretch. The surface along which the elevator car is conveyed on the rail stretch is termed a guide surface. The receiver is placed on, for example, the guide surface of the installed rail stretch. The transmitters transmit radio signals to the receiver similarly to a GPS (Global Positioning System).
In advantageous forms of embodiment additional sensors detect freely selectable locations such as rail fastenings, rail straps, floor stopping points or positions of the shaft doors, as soon as the receiver passes the level thereof in the elevator shaft. Advantageously, an acceleration sensor for detection of acceleration forces in the elevator car is provided. This further detection advantageously takes place simultaneously with the determination of the position of the guide surface.
In the measuring operation the receiver detects, preferably continuously and while it is moved along the guide surface of the rail stretch over the entire length of the rail stretch, the spacings from the individual transmitters or in each instance the position of rail fastenings, rail straps and shaft doors with respect to the displacement path of the receiver. The receiver preferably ascertains spacing data, i.e. the instantaneous spacing from the transmitters, on the basis of the detected radio signals. These spacing data are ascertained, for example, incrementally per unit of length and unit of time.
The resulting spacing data are preferably passed on to the evaluating unit. The evaluating unit compares the spacing data with reference data of the spacing of the receiver from the transmitters. Such reference data are, for example, ascertained in a calibration process and stored. This comparison delivers, as the result, departures from the rectilinearity of the rail stretch. This result can be represented, for example, graphically as a curvature in three dimensions. An advantageous result of the evaluation is a correction protocol, in accordance with which the engineers can straighten the individual guide rails of the rail stretch. Equipped with precise diagrams, as also straightening proposals, the engineer can precisely realign the rail stretch and this rapidly achieves or maintains an optimum travel behavior of the elevator car.